Magnesium alloy with high strength and toughness and controllable degradation, preparation method and application thereof

Abstract

The present invention provides a magnesium alloy with high strength and toughness and controllable degradation, as well as a preparation method and application thereof. The magnesium alloy comprises, by mass percentage, the following: Zn: 2% to 3.5%, Ca: 0.5% to 1.0%, Zr: 0.2% to 0.35%, with the remainder being magnesium and unavoidable impurities. The present invention effectively improves the extrusion forming performance and structural uniformity of the alloy by simultaneously adding zirconium, zinc and calcium elements to the magnesium alloy, thereby enhancing the mechanical strength, toughness and corrosion resistance of the magnesium alloy. The present invention homogenizes the structure of the ingot and performs appropriate porous hot extrusion treatment, and then performs multiple passes of room temperature cold drawing and high-density pulse current treatment on the ingot, thereby enabling the strength and plastic toughness of the alloy to be simultaneously improved, and significantly reducing the degradation rate of the product. The present invention provides an efficient and energy-saving preparation technology for the development of high-performance, corrosion-resistant biomedical magnesium alloys, giving magnesium alloys broad prospects in the fields of orthopedics and medical implant materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedical magnesium alloy implant materials, and in particular relates to a Mg-Zn-Zr-Ca biomedical magnesium alloy material with high strength and toughness and uniform and controllable degradation, as well as a preparation method and application thereof. Background Art

[0002] Currently, traditional metal implants in clinical use primarily consist of stainless steel, cobalt-based alloys, and titanium alloys. These materials offer excellent mechanical properties and corrosion resistance. However, their elastic modulus differs significantly from that of natural bone, potentially causing stress shielding during use and hindering bone healing. Furthermore, these metal materials are often inert, requiring secondary surgery to remove them after fracture healing, adding to the patient's pain and financial burden.

[0003] Magnesium alloys offer advantages such as low density, low elastic modulus, biodegradability, high specific strength, and good biocompatibility. As a candidate material for biodegradable implantable devices, they show great potential in medical fields such as orthopedics and cardiovascular medicine. In recent years, research on biodegradable magnesium alloys in the medical field has increased significantly and garnered widespread attention. Compared to traditional stainless steel, cobalt-based alloys, and titanium alloy orthopedic implants, magnesium alloy implants not only degrade and absorb after damaged bone tissue repair, eliminating the need for secondary surgical removal, significantly reducing patient pain and treatment costs. Furthermore, the density and elastic modulus of magnesium alloys are closer to those of human bone tissue, significantly reducing stress shielding and promoting bone healing. However, the rapid degradation of magnesium and its alloys in the body and their poor mechanical strength and toughness have severely hampered the widespread application of magnesium alloys in orthopedics and other medical fields. Therefore, improving the corrosion resistance and mechanical strength of medical magnesium alloys is a pressing issue for biomedical magnesium alloys. Summary of the Invention

[0004] In response to the problems of insufficient strength and toughness and uncontrollable degradation rate of existing biomedical magnesium alloys, the present invention provides a magnesium alloy with high strength and toughness and controllable degradation, as well as its preparation method and application. The magnesium alloy has a tensile strength of 320-350 MPa, a yield strength of 240-263 MPa, and an elongation at break of 23-30%. The corrosion rate is as low as 0.15-0.23 mg / cm 2 / day, and has good biocompatibility and controllable degradation properties.

[0005] Specifically, the present invention designs and develops a biomedical magnesium alloy with high strength, toughness and controllable degradation. By simultaneously adding zirconium, zinc and calcium elements to the magnesium alloy, the extrusion forming performance and structural uniformity of the alloy are effectively improved, thereby enhancing the mechanical strength, toughness and corrosion resistance of the magnesium alloy.

[0006] The present invention also proposes a method for preparing a biomedical magnesium alloy with high strength, toughness and controllable degradation. By homogenizing the ingot and subjecting it to appropriate porous hot extrusion treatment, and then subjecting it to multiple passes of room temperature cold drawing and high-density pulse current treatment, the strength and plasticity of the alloy can be simultaneously improved, and the degradation rate of the product can be significantly reduced.

[0007] The present invention attempts for the first time to combine hot and cold large plastic deformation of a magnesium alloy with appropriate additions of Zr, Zn and Ca with instantaneous high-density pulse current treatment, and through the adjustment of components and process parameters, achieves a significant improvement in the comprehensive mechanical properties of the product and uniform and controllable degradation.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The invention provides a Mg-Zn-Zr-Ca magnesium alloy with high strength and toughness and controllable degradation. The magnesium alloy comprises, by mass percentage, 2% to 3.5% Zn, 0.5% to 1.0% Ca, 0.2% to 0.35% Zr, and the remainder being Mg and impurities.

[0010] Optionally, the impurities include, by mass percentage: Al≤0.02%, Cu≤0.01%, Ni≤0.02%.

[0011] Optionally, the magnesium alloy has a tensile strength of 320-350 MPa, a yield strength of 240-263 MPa, and an elongation of 23-30%. In SBF simulated body fluid, the average corrosion rate is as low as 0.15-0.23 mg / cm 2 / day.

[0012] The present invention also provides a method for preparing a Mg-Zn-Zr-Ca magnesium alloy having high strength and toughness and controllable degradation, comprising the following steps:

[0013] S1: Deoxidize and clean the surfaces of raw materials high-purity magnesium ingots, high-purity zinc ingots, Mg-Zr master alloys and Mg-Ca master alloys;

[0014] S2: First, a crucible is placed in a resistance furnace for preheating, and then an inert protective gas is introduced into the furnace. A magnesium ingot and a zinc ingot are placed in the crucible, and the furnace temperature is increased to completely melt the magnesium ingot and the zinc ingot, and slag treatment is performed; then, a Mg-Zr master alloy and a Mg-Ca master alloy are added to the crucible; after the alloy material is melted, the mixture is stirred, allowed to stand for slag removal, and then the melt is poured into a copper mold. After solidification, the mold is removed to obtain a magnesium alloy ingot;

[0015] S3: cutting and homogenizing the magnesium alloy ingot, and hot-extruding the ingot into rods by graded hot extrusion;

[0016] S4: processing the rod into a wire of predetermined size through room temperature cold drawing and multi-stage tempering process;

[0017] S5: The wire is treated with a high-energy pulse current to cause static recrystallization in a very short time, thereby obtaining the magnesium alloy having high strength and toughness and controllable degradation.

[0018] Preferably, the Mg-Zr master alloy includes a Mg-20% Zr master alloy; and the Mg-Ca master alloy includes a Mg-30% Ca master alloy.

[0019] Preferably, step S2 comprises: under inert gas protection conditions, melting magnesium ingots and zinc ingots at 700-720°C, keeping warm for 30-60 minutes, then heating to 750-760°C, adding Mg-Zr master alloy and Mg-Ca master alloy, stirring for 8-15 minutes after melting, and refining for 25-30 minutes. After refining, heating to 760-790°C and standing for 40-50 minutes, and casting into the magnesium alloy ingot at 710-720°C.

[0020] Preferably, in step S3, the homogenization treatment conditions include: raising the temperature to 350°C in a resistance heating furnace, keeping the temperature for 2 hours, then raising the temperature to 420°C and keeping the temperature for 24 hours, and then quenching and cooling in water at 30-50°C.

[0021] Preferably, in step S3, the hot extrusion conditions include: an extrusion temperature of 350-380° C., an extrusion ratio of 14:1, and an extrusion speed of 0.2-1 mm / s.

[0022] Preferably, in step S4, the conditions of the room temperature drawing and multi-stage tempering include: the tempering temperature of each pass is 100-200° C., and the tempering time is 30-60 min.

[0023] Preferably, in step S5, the current parameter conditions of the high energy pulse current include: a peak current density of 1.0×10 10 ~1.3×10 10 A / m 2 , pulse width: 20~60μs, pulse frequency: 100~150Hz, pulse processing time: 30s~600s, duty cycle: 0.002~0.006.

[0024] The present invention also provides the use of the Mg-Zn-Zr-Ca magnesium alloy with high strength and toughness and controllable degradation in biomedical metal sutures and biomedical implant devices.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] For example, the present invention combines hot and cold large plastic deformation of a magnesium alloy with appropriate additions of Zr, Zn and Ca with instantaneous high-density pulse current treatment, and through the adjustment of components and process parameters, achieves a significant improvement in the comprehensive mechanical properties of the magnesium alloy and uniform and controllable degradation, i.e., uniform and controllable corrosion.

[0027] For another example, the magnesium alloy prepared by the present invention using high-density current narrow pulse width combined with room temperature cold drawing technology has an ultrafine grain structure; through the formation of a uniform ultrafine grain structure, the random orientation distribution characteristics of the weak texture and the dispersed distribution of nano-sized CaMgZn phases, the obtained magnesium alloy material has high strength (tensile strength of 320-350 MPa) and high plasticity (elongation of 23-30%); thereby, tissue segregation and grain growth can be effectively inhibited, thereby obtaining excellent properties with high strength and toughness, uniform and controllable degradation, and can be widely used in the preparation of medical sutures and bone nails.

[0028] For another example, the magnesium alloy provided by the present invention has good biocompatibility and controllable degradation performance; the added Zn and Ca elements are both nutritional elements beneficial to human functions and can be absorbed by the human body; the Zr element can also effectively refine the grains and improve the uniform and controllable degradation performance.

[0029] For example, the method for preparing a magnesium alloy with high strength and toughness and controllable degradation provided by the present invention has a simple and efficient process. Under high-energy pulse current treatment, it can achieve complete recrystallization and grain refinement within 30 seconds, and can be completed in one go. It is also easy to prepare magnesium alloy products with a clean surface, few impurities, and large size, and can quickly realize large-scale process production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the SEM microstructure of the magnesium alloy obtained in Example 1 after being treated with pulse current;

[0031] Figure 2 This is the metallographic microstructure diagram of the magnesium alloy obtained in Example 2 after pulse current treatment.

[0032] Figure 3 This is the metallographic microstructure diagram of the magnesium alloy obtained in Example 3 after pulse current treatment.

[0033] Figure 4 This is a metallographic microstructure diagram of the magnesium alloy obtained in Example 4 after pulse current treatment.

[0034] Figure 5 This is the metallographic microstructure of the magnesium alloy obtained in Comparative Example 1 after pulse current treatment.

[0035] Figure 6This is the metallographic microstructure diagram of the magnesium alloy obtained in Comparative Example 2 after pulse current treatment. DETAILED DESCRIPTION

[0036] To make the objectives, features, and beneficial effects of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described below are intended only to illustrate the present invention and are not intended to limit the present invention. Furthermore, descriptions of identical or similar elements between different embodiments, as well as descriptions of prior art elements, features, and effects, may be omitted.

[0037] Example 1

[0038] This embodiment provides a magnesium alloy with high strength and toughness and controllable degradation, wherein the mass percentages of the Mg-Zn-Zr-Ca alloy elements are: Zn is 3%, Zr is 0.3%, Ca is 0.5%, Al is 0.003%, Ni is 0.002%, Cu is 0.003%, and the balance is Mg.

[0039] The raw materials are: Mg ingots with a purity of 99.994%, Zn ingots with a purity of 99.996%, Mg-Zr master alloy with a Zr mass percentage of 20.2% (impurity mass percentage of 0.002%), and Mg-Ca master alloy with a Ca mass percentage of 29.9% (impurity mass percentage of 0.005%).

[0040] The preparation method of the magnesium alloy is as follows:

[0041] S1, deoxidizing and cleaning the surfaces of the raw materials high-purity Mg ingot, high-purity Zn ingot, Mg-Zr master alloy and Mg-Ca master alloy;

[0042] S2, preparing raw materials by mass percentage, melting magnesium ingots and zinc ingots in a vacuum melting furnace at 720°C under inert gas protection, holding the temperature for 50 minutes, then heating to 750°C and adding Mg-Zr master alloy and Mg-Ca master alloy, stirring for 10 minutes after melting, and refining for 30 minutes. After refining, heating to 760°C and standing for 40 minutes, and then casting into ingots at 720°C;

[0043] S3, cutting the above ingot into bars with a diameter of 60 mm, raising the temperature to 350°C in a resistance heating furnace, holding the temperature for 2 hours, then raising the temperature to 420°C and holding the temperature for 24 hours, and then quenching and cooling in 50°C water; the homogenized alloy bars are subjected to graded hot extrusion treatment in a press, and extruded into bars with a diameter of 4 mm at an extrusion temperature of 350°C and an extrusion speed of 0.2 mm / s, with an extrusion ratio of 14:1;

[0044] S4, drawn into a wire with a diameter of 0.8 mm through multiple passes at room temperature, with each pass tempering temperature of 150 °C and tempering time of 40 min;

[0045] In S5, the drawn wire is subjected to high-energy pulse current treatment with a current density of 1.2×10 10 A / m 2 , the pulse width is 30μs, the pulse frequency is 150Hz, the pulse processing time is 60s, and the duty cycle is 0.003.

[0046] The microstructure of the magnesium alloy wire is as follows Figure 1 As shown, it can be seen that the average grain size of the magnesium alloy can be refined to about 1.5 μm, and the structure is uniform.

[0047] The room temperature tensile strength of this magnesium alloy can reach 350MPa, the yield strength is 263MPa, and the elongation is 30%. The average corrosion rate in Hank's simulated body fluid is 0.15mg / cm 2 / day, the corrosion mode is uniform corrosion. The corrosion resistance of the alloy is improved by more than 50% compared with the cast alloy.

[0048] In the present invention, the mechanical properties are tested by tensile testing. Tensile specimens in different states are subjected to tensile testing on an AGS-X-20KND universal testing machine. The processing and experimental process of the room temperature tensile test specimens are carried out in accordance with the "Metallic Materials Room Temperature Tensile Test Method" (GB / T288-2002). The specimens are processed by wire cutting machine, and the tensile strain rate is set to 1×10 -3 s -1 To ensure more accurate tensile test results, the sample must be polished before testing to prevent traces left by the machining process from affecting the measured properties. To ensure the accuracy of the experimental data and eliminate the possibility of accidental errors during the experiment, the tensile test is conducted on the sample at least three times under the same conditions and the average value is calculated. The main purpose of the tensile test is to calculate the sample's yield strength, tensile strength, elongation, etc.

[0049] The corrosion rate was measured by weight loss method. The corrosion solution used was SBF to simulate body fluid. The surface oxide layer of the sample was removed before immersion and ultrasonic cleaning and drying were performed. The weight before immersion was recorded. The surface area of the sample and the volume of the solution were measured by 1 cm 2 The ratio of 1:20ml was used, and the corrosion solution was replaced every 48 hours. The samples were taken out after soaking for one week, and the degradation products were removed with a mixed solution of silver nitrate and chromic acid. The samples were then washed with deionized water. After drying the samples, the residual samples were weighed and the degradation rate was calculated.

[0050] Table 1 SBF simulated body fluid reagent ratio (100ml)

[0051]

[0052]

[0053] Example 2

[0054] This embodiment provides a magnesium alloy with high strength and toughness and controllable degradation, wherein the mass percentages of the Mg-Zn-Zr-Ca alloy elements are: Zn is 2%, Zr is 0.35%, Ca is 0.7%, Al is 0.02%, Ni is 0.02%, Cu is 0.006%, and the balance is Mg.

[0055] The raw materials are: Mg ingots with a purity of 99.993%, Zn ingots with a purity of 99.995%, Mg-Zr master alloy with a Zr mass percentage of 19.7% (impurity mass percentage of 0.002%), and Mg-Ca master alloy with a Ca mass percentage of 29.7% (impurity mass percentage of 0.005%).

[0056] The preparation method of the magnesium alloy is as follows:

[0057] S1, deoxidizing and cleaning the surfaces of the raw materials high-purity Mg ingot, high-purity Zn ingot, Mg-Zr master alloy and Mg-Ca master alloy;

[0058] S2, preparing raw materials by mass percentage, melting magnesium ingots and zinc ingots in a vacuum melting furnace at 700°C under inert gas protection, holding the temperature for 60 minutes, then heating to 760°C, adding Mg-Zr master alloy and Mg-Ca master alloy, stirring for 15 minutes after melting, and refining for 25 minutes. After refining, heating to 780°C, standing for 50 minutes, and casting into ingots at 710°C;

[0059] S3, cutting the above ingot into bars with a diameter of 60 mm, raising the temperature to 350°C in a resistance heating furnace, holding the temperature for 2 hours, then raising the temperature to 420°C and holding the temperature for 24 hours, and then quenching and cooling in 30°C water; the homogenized alloy bars are subjected to graded hot extrusion treatment in a press, and extruded into bars with a diameter of 4 mm at an extrusion temperature of 380°C and an extrusion speed of 0.5 mm / s, with an extrusion ratio of 14:1;

[0060] S4, drawn into a wire with a diameter of 0.6 mm through multiple passes at room temperature, with each pass tempering temperature of 200 °C and tempering time of 30 min;

[0061] In S5, the drawn wire is subjected to high-energy pulse current treatment with a current density of 1.3×10 10 A / m 2, the pulse width is 20μs, the pulse frequency is 100Hz, the pulse processing time is 300s, and the duty cycle is 0.002.

[0062] The microstructure of the magnesium alloy wire is as follows Figure 2 As shown, it can be seen that the average grain size is about 2.5 μm and the structure is uniform.

[0063] The test methods for the tensile strength, yield strength, elongation and corrosion rate of the magnesium alloy refer to Example 1.

[0064] The room temperature tensile strength of this magnesium alloy can reach 342MPa, the yield strength is 248MPa, and the elongation is 23%. The average corrosion rate in Hank's simulated body fluid is 0.18mg / cm 2 / day, the corrosion mode is uniform corrosion. The corrosion resistance of the alloy is improved by more than 40% compared with the cast alloy.

[0065] Example 3

[0066] This embodiment provides a magnesium alloy with high strength and toughness and controllable degradation, wherein the mass percentages of the Mg-Zn-Zr-Ca alloy elements are: Zn: 3.5%, Zr: 0.2%, Ca: 1%, Al: 0.01%, Ni: 0.01%, Cu: 0.01%, and the balance is Mg;

[0067] The raw materials are: Mg ingots with a purity of 99.994%, Zn ingots with a purity of 99.996%, Mg-Zr master alloy with a Zr mass percentage of 20.2% (impurity mass percentage of 0.002%), and Mg-Ca master alloy with a Ca mass percentage of 29.9% (impurity mass percentage of 0.005%).

[0068] The preparation method of the magnesium alloy is as follows:

[0069] S1, deoxidizing and cleaning the surfaces of the raw materials high-purity Mg ingot, high-purity Zn ingot, Mg-Zr master alloy and Mg-Ca master alloy;

[0070] S2, preparing raw materials by mass percentage, melting magnesium ingots and zinc ingots in a vacuum melting furnace at 710°C under inert gas protection, holding the temperature for 30 minutes, then heating to 755°C, adding Mg-Zr master alloy and Mg-Ca master alloy, stirring for 8 minutes after melting, and refining for 28 minutes. After refining, heating to 790°C, standing for 45 minutes, and casting into ingots at 715°C;

[0071] S3, cutting the above ingot into bars with a diameter of 60 mm, raising the temperature to 350°C in a resistance heating furnace, holding the temperature for 2 hours, then raising the temperature to 420°C and holding the temperature for 24 hours, and then quenching and cooling in 40°C water; the homogenized alloy bars are subjected to graded hot extrusion treatment in a press, and extruded into bars with a diameter of 4 mm at an extrusion temperature of 370°C and an extrusion speed of 1.0 mm / s, with an extrusion ratio of 14:1;

[0072] S4, drawn into a wire with a diameter of 0.8 mm through multiple passes at room temperature, with each pass tempering temperature of 100 °C and tempering time of 60 min;

[0073] S5, the drawn wire is subjected to high-energy pulse current treatment with a current density of 1.0×10 10 A / m 2 , the pulse width is 40μs, the pulse frequency is 130Hz, the pulse processing time is 600s, and the duty cycle is 0.004.

[0074] The wire microstructure of the alloy is as follows Figure 3 As shown, the average grain size of the alloy can be refined to about 2.8μm; the structure is uniform.

[0075] The test methods for the tensile strength, yield strength, elongation and corrosion rate of the magnesium alloy refer to Example 1.

[0076] The room temperature tensile strength of the alloy can reach 330MPa, the yield strength is 245MPa, and the elongation is 27%. The average corrosion rate in Hank's simulated body fluid is 0.20mg / cm 2 / day, the corrosion mode is uniform corrosion. The corrosion resistance of the alloy is improved by more than 35% compared with the cast alloy.

[0077] Example 4

[0078] This embodiment provides a magnesium alloy, wherein the mass percentages of the Mg-Zn-Zr-Ca alloy elements are: 3.5% Zn, 0.3% Zr, 0.5% Ca, 0.005% Al, 0.005% Ni, 0.005% Cu, and the remainder is Mg.

[0079] The raw materials are: Mg ingots with a purity of 99.994%, Zn ingots with a purity of 99.996%, Mg-Zr master alloy with a Zr mass percentage of 20.2% (impurity mass percentage of 0.002%), and Mg-Ca master alloy with a Ca mass percentage of 29.9% (impurity mass percentage of 0.005%).

[0080] The preparation method of the magnesium alloy is as follows:

[0081] S1, deoxidizing and cleaning the surfaces of the raw materials high-purity Mg ingot, high-purity Zn ingot, Mg-Zr master alloy and Mg-Ca master alloy;

[0082] S2, preparing raw materials by mass percentage, melting magnesium ingots and zinc ingots in a vacuum melting furnace at 720°C under inert gas protection, holding the temperature for 50 minutes, then heating to 750°C and adding Mg-Zr master alloy and Mg-Ca master alloy, stirring for 10 minutes after melting, and refining for 30 minutes. After refining, heating to 760°C and standing for 40 minutes, and then casting into ingots at 720°C;

[0083] S3, cutting the above ingot into bars with a diameter of 60 mm, raising the temperature to 350°C in a resistance heating furnace, holding the temperature for 2 hours, then raising the temperature to 420°C and holding the temperature for 24 hours, and then quenching and cooling in 50°C water; the homogenized alloy bars are subjected to graded hot extrusion treatment in a press, and extruded into bars with a diameter of 4 mm at an extrusion temperature of 350°C and an extrusion speed of 0.2 mm / s, with an extrusion ratio of 14:1;

[0084] S4, drawn into a wire with a diameter of 0.8 mm through multiple passes at room temperature, with each pass tempering temperature of 150 °C and tempering time of 40 min;

[0085] In S5, the drawn wire is subjected to high-energy pulse current treatment with a current density of 1.2×10 10 A / m 2 , the pulse width is 60μs, the pulse frequency is 150Hz, the pulse processing time is 30s, and the duty cycle is 0.006.

[0086] The wire microstructure of the alloy is as follows Figure 4 As shown, the average grain size of the alloy can be refined to about 3.2μm; the structure is uniform.

[0087] The test methods for the tensile strength, yield strength, elongation and corrosion rate of the magnesium alloy refer to Example 1.

[0088] The room temperature tensile strength of the alloy can reach 320MPa, the yield strength is 240MPa, and the elongation is 25%. The average corrosion rate in Hank's simulated body fluid is 0.23mg / cm 2 / day, the corrosion mode is uniform corrosion.

[0089] Comparative Example 1

[0090] This embodiment provides a magnesium alloy, wherein the mass percentages of the Mg-Zn-Zr-Ca alloy elements are: 3% Zn, 0.3% Zr, 0.5% Ca, 0.003% Al, 0.002% Ni, 0.003% Cu, and the remainder is Mg.

[0091] The raw materials are: Mg ingots with a purity of 99.994%, Zn ingots with a purity of 99.996%, Mg-Zr master alloy with a Zr mass percentage of 20.2% (impurity mass percentage of 0.002%), and Mg-Ca master alloy with a Ca mass percentage of 29.9% (impurity mass percentage of 0.005%).

[0092] The preparation method of the magnesium alloy is as follows:

[0093] S1, deoxidize the surface of the raw material and clean it;

[0094] S2, preparing raw materials by mass percentage, melting magnesium ingots and zinc ingots in a vacuum melting furnace at 720°C under inert gas protection, holding the temperature for 50 minutes, then heating to 750°C and adding Mg-Zr master alloy and Mg-Ca master alloy, stirring for 10 minutes after melting, and refining for 30 minutes. After refining, heating to 760°C and standing for 40 minutes, and then casting into ingots at 720°C;

[0095] S3, cutting the above ingot into bars with a diameter of 60 mm, raising the temperature to 350°C in a resistance heating furnace, holding the temperature for 2 hours, then raising the temperature to 420°C and holding the temperature for 24 hours, and then quenching and cooling in 50°C water; the homogenized alloy bars are subjected to graded hot extrusion treatment in a press, and extruded into bars with a diameter of 4 mm at an extrusion temperature of 350°C and an extrusion speed of 0.2 mm / s, with an extrusion ratio of 14:1;

[0096] S4, at room temperature, is drawn into a wire with a diameter of 0.8 mm through multiple passes, with a tempering temperature of 150°C and a tempering time of 40 min per pass.

[0097] The wire microstructure of the alloy is as follows Figure 5 As shown, the average grain size of the alloy can be refined to about 6.0 μm.

[0098] The test methods for the tensile strength, yield strength, elongation and corrosion rate of the magnesium alloy refer to Example 1.

[0099] The room temperature tensile strength of the alloy can reach 370MPa, the yield strength is 293MPa, and the elongation is 10%. The average corrosion rate in Hank's simulated body fluid is 0.26mg / cm 2 / day, the corrosion mode is uneven corrosion.

[0100] Comparative Example 2

[0101] This embodiment provides a magnesium alloy, wherein the mass percentages of the Mg-Zn-Zr-Ca alloy elements are as follows: 3% Zn, 0.3% Zr, 0.5% Ca, 0.003% Al, 0.002% Ni, 0.003% Cu, and the balance Mg;

[0102] The raw materials are: Mg ingots with a purity of 99.994%, Zn ingots with a purity of 99.996%, Mg-Zr master alloy with a Zr mass percentage of 20.2% (impurity mass percentage of 0.002%), and Mg-Ca master alloy with a Ca mass percentage of 29.9% (impurity mass percentage of 0.005%).

[0103] The preparation method of the magnesium alloy is as follows:

[0104] S1, deoxidize the surface of the raw material and clean it;

[0105] S2, preparing raw materials by mass percentage, melting magnesium ingots and zinc ingots in a vacuum melting furnace at 720°C under inert gas protection, holding the temperature for 50 minutes, then heating to 750°C and adding Mg-Zr master alloy and Mg-Ca master alloy, stirring for 10 minutes after melting, and refining for 30 minutes. After refining, heating to 760°C and standing for 40 minutes, and then casting into ingots at 720°C;

[0106] S3, cutting the above ingot into bars with a diameter of 60 mm, raising the temperature to 350°C in a resistance heating furnace, holding the temperature for 2 hours, then raising the temperature to 420°C and holding the temperature for 24 hours, and then quenching and cooling in 50°C water; the homogenized alloy bars are subjected to graded hot extrusion treatment in a press, and extruded into bars with a diameter of 4 mm at an extrusion temperature of 350°C and an extrusion speed of 0.2 mm / s, with an extrusion ratio of 14:1;

[0107] S4, drawn into a wire with a diameter of 0.8 mm through multiple passes at room temperature, with each pass tempering temperature of 150 °C and tempering time of 40 min;

[0108] S5, the wire is subjected to conventional heat treatment (annealing treatment) at 200°C for 30 hours, and then air-cooled.

[0109] The wire microstructure of the alloy is as follows Figure 6 As shown, the average grain size of the alloy can be refined to about 5.0 μm.

[0110] The test methods for the tensile strength, yield strength, elongation and corrosion rate of the magnesium alloy refer to Example 1.

[0111] The room temperature tensile strength of the alloy can reach 295MPa, the yield strength is 203MPa, and the elongation is 18%. The average corrosion rate in Hank's simulated body fluid is 0.30mg / cm 2 / day, the corrosion mode is uneven corrosion.

[0112] Results comparison

[0113] A comparative analysis of the microstructures and properties of the magnesium alloys obtained in Example 1 and Comparative Example 1 revealed that the Mg-Zn-Zr-Ca alloy in Comparative Example 1, which had not undergone high-energy pulse current treatment, had large and uneven grains and contained a large number of deformation twins, which were detrimental to improving the alloy's plasticity, workability, and corrosion resistance. Mechanical and corrosion resistance tests showed that the ductility, toughness, and corrosion resistance of the alloy in Comparative Example 1 were significantly lower than those of the alloy in Example 1.

[0114] A comparative analysis of the microstructures and properties of the magnesium alloys obtained in Example 1 and Comparative Example 2 revealed that the cold-drawn Mg-Zn-Zr-Ca alloy in Comparative Example 2 exhibited abnormally large grain size after conventional heat treatment, resulting in reduced mechanical properties and corrosion resistance. Mechanical and corrosion resistance testing revealed that the mechanical properties and corrosion resistance of Comparative Example 2 were significantly lower than those of the alloy in Example 1.

[0115] The performance comparison of each embodiment and comparative example is shown in the following table:

[0116] Table 2: Microstructure, mechanical properties and corrosion properties of each embodiment and comparative example

[0117]

[0118] In summary, the magnesium alloy with a uniform ultrafine grain structure prepared by the present invention has a special microstructure. After the grain size is refined and controlled, a biomedical magnesium alloy with simultaneously improved high strength and high plasticity and toughness is obtained, which greatly improves its processing and forming performance and can be used to design and manufacture magnesium alloy implant devices with complex structures. In addition, the method improves the corrosion resistance of the magnesium alloy and realizes the uniform and controllable degradation of the magnesium alloy, providing an efficient and energy-saving processing technology for the development of high-performance, corrosion-resistant biomedical magnesium alloys, which makes the magnesium alloy have broad development prospects in the field of orthopedics and medical implant materials.

[0119] Although specific embodiments have been described above, these embodiments are not intended to limit the scope of the present disclosure, even when only a single embodiment is described with respect to specific features. The feature examples provided in the present disclosure are intended to be illustrative, not limiting, unless otherwise stated. In specific implementations, the technical features of one or more dependent claims may be combined with the technical features of the independent claims, depending on actual needs and where technically feasible, and the technical features from the corresponding independent claims may be combined in any appropriate manner rather than solely through the specific combinations listed in the claims.

[0120] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A method for preparing a magnesium alloy with high strength and toughness and controllable degradation, characterized in that: The magnesium alloy comprises, by mass percentage, 2% to 3.5% Zn, 0.5% to 1.0% Ca, 0.2% to 0.35% Zr, and the remainder Mg and impurities. The impurities comprise, by mass percentage, Al ≤ 0.02%, Cu ≤ 0.01%, and Ni ≤ 0.02%. The magnesium alloy has a tensile strength of 320 to 350 MPa, a yield strength of 240 to 263 MPa, and an elongation of 23 to 30%. In SBF simulated body fluid, the corrosion rate is as low as 0.15 to 0.23 mg / cm 2 / day; the preparation method comprises the following steps: S1: Deoxidize and clean the surfaces of raw materials such as magnesium ingots, zinc ingots, Mg-Zr master alloys and Mg-Ca master alloys; S2: First, a crucible is placed in a resistance furnace for preheating, and then an inert protective gas is introduced into the furnace. A magnesium ingot and a zinc ingot are placed in the crucible, and the furnace temperature is increased to completely melt the magnesium ingot and the zinc ingot, and slag treatment is performed; then, a Mg-Zr master alloy and a Mg-Ca master alloy are added to the crucible; after the alloy material is melted, the mixture is stirred, allowed to stand for slag removal, and then the melt is poured into a copper mold. After solidification, the mold is removed to obtain a magnesium alloy ingot; S3: cutting and homogenizing the magnesium alloy ingot, and hot extruding the ingot into a rod; S4: Processing the rod into a wire of predetermined size through multiple drawing and tempering processes at room temperature; S5: treating the wire with a high-energy pulse current to cause static recrystallization in a very short time, thereby obtaining the magnesium alloy having high strength and toughness and controllable degradation; In the step S4, tempering is performed after each drawing pass, the tempering temperature is 100°C to 200°C, and the tempering time is 30 to 60 minutes; In step S5, the conditions for the high energy pulse current treatment include: a peak current density of 1.0×10 10 ~1.3×10 10 A / m 2 , the pulse width is 20~60μs, the pulse frequency is 100~150Hz, the pulse processing time is 30s~600s, and the duty cycle is 0.002~0.

006.

2. The preparation method according to claim 1, wherein The step S2 comprises: under inert gas protection conditions, melting magnesium ingots and zinc ingots at 700-720° C., keeping the temperature for 30-60 minutes, then heating to 750-760° C., adding Mg-Zr master alloy and Mg-Ca master alloy, stirring for 8-15 minutes after melting, and refining for 25-30 minutes. After refining, heating to 760-790° C., standing for 40-50 minutes, and casting the magnesium alloy ingot at 710-720° C.

3. The preparation method according to claim 1, wherein In step S3, the homogenization treatment conditions include: raising the temperature to 350° C. in a resistance heating furnace, keeping the temperature for 2 hours, then raising the temperature to 420° C., keeping the temperature for 24 hours, and then quenching in 30-50° C. water.

4. The preparation method according to claim 1, wherein In step S3, the hot extrusion conditions include: an extrusion temperature of 350-380° C., an extrusion ratio of 14:1, and an extrusion speed of 0.2-1 mm / s.

5. Use of a magnesium alloy obtained by the method for preparing a magnesium alloy with high strength and toughness and controllable degradation as claimed in any one of claims 1 to 4 in a biomedical metal suture or a biomedical implant device.

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